Handle inheritance properly, there was different behavior depending o…

…n whether or not AASM was included in the child class or not.

(cherry picked from commit 48ff9a5)

lib/aasm.rb

@@ -15,12 +15,11 @@ class UndefinedState < RuntimeError
   end
 
   def self.included(base) #:nodoc:
-    # TODO - need to ensure that a machine is being created because
-    # AASM was either included or arrived at via inheritance.  It
-    # cannot be both.
     base.extend AASM::ClassMethods
     AASM::Persistence.set_persistence(base)
-    AASM::StateMachine[base] = AASM::StateMachine.new('')
+    unless AASM::StateMachine[base]
+      AASM::StateMachine[base] = AASM::StateMachine.new('')
+    end
   end
 
   module ClassMethods

spec/unit/aasm_spec.rb

@@ -27,6 +27,11 @@ def exit
   end
 end
 
+class FooTwo < Foo
+  include AASM
+  aasm_state :foo
+end
+
 class Bar
   include AASM
 
@@ -82,20 +87,14 @@ def rich?; self.balance >= RICH; end
 
 
 describe AASM, '- subclassing' do
-  before(:each) do
-    @parent = Class.new do
-      include AASM
+  it 'should have the parent states' do
+    Foo.aasm_states.each do |state|
+      FooTwo.aasm_states.should include(state)
     end
   end
-
-  it 'should invoke the original inherited callback' do
-    @parent.should_receive(:inherited)
-    Class.new(@parent)
-  end
-
-  it 'should have a unique states hash' do
-    child = Class.new(@parent)
-    child.aasm_states.equal?(@parent.aasm_states).should be_false
+
+  it 'should not add the child states to the parent machine' do
+    Foo.aasm_states.should_not include(:foo)
   end
 end